/***************************************************************************

					-= Seta, Sammy, Visco (SSV) System =-

					driver by	Luca Elia (l.elia@tin.it)

	This hardware only generates sprites. But they're of various types,
	including some large "floating tilemap" ones.

	Sprites RAM is 0x40000 bytes long. The first 0x2000 bytes hold a list
	of sprites to display (the list can be made shorter using an end-of-list
	marker).

	Each entry in the list (8 bytes) is a multi-sprite (e.g it tells the
	hardware to display up to 32 single-sprites).

	The list looks like this:

	Offset: 	Bits:					Value:

		0.w		f--- ---- ---- ----		Shadow (Highlight?)
				-edc ---- ---- ----		Each bit enables 2 bitplanes*
				---- ba-- ---- ----		X Size (1,2,4,8 tiles)
				---- --98 ---- ----		Y Size (1,2,4,8 tiles)
				---- ---- 765- ----		Index of a scroll to apply to the single-sprite(s)
				---- ---- ---4 3210		Number of single-sprites, minus 1

		2.w		f--- ---- ---- ----		List end
				-edc ba98 7654 3210		Offset of the single-sprite(s) data

		4.w		fedc ba-- ---- ----
				---- --98 7654 3210		X displacement (ignored by tilemap sprites?)

		4.w		fedc ba-- ---- ----
				---- --98 7654 3210		Y displacement (ignored by tilemap sprites?)


* bit c, which enables/disables the 2 high order bitplanes (256 / 64 color tiles)
  is the only one implemented. Needed by keithlcy (logo), drifto94 (wheels).

	A single-sprite can be:

	1. a rectangle of tiles (only 1 tile code needs to be specified)
	2. a row of tiles of a tilemap in ram. The row is (always?) as wide
	   as the screen and 64 pixels tall.

	Rectangle case(1):
	Offset: 	Bits:					Value:

		0.w								Code (low bits)

		2.w		f--- ---- ---- ----		Flip X
				-e-- ---- ---- ----		Flip Y
				--dc ba-- ---- ----		Code (high bits)
				---- --9- ---- ----		Code? Color?
				---- ---8 7654 3210		Color code (64 color steps)

		4.w		f--- ---- ---- ----		Shadow (Highlight?)
				-edc ---- ---- ----		Each bit enables 2 bitplanes*
				---- ba-- ---- ----		X Size (1,2,4,8 tiles)
				---- --98 7654 3210		X

		6.w		fedc ---- ---- ----
				---- ba-- ---- ----		Y Size (1,2,4 tiles) **
				---- --98 7654 3210		Y


	Tilemap case(2):
	Offset: 	Bits:					Value:

		0.w		fedc ba98 7654 3---
				---- ---- ---- -210		Scroll index (see below)

		2.w								Always 0

		4.w		fedc ba-- ---- ----
				---- --98 7654 3210		X?

		6.w		fedc ---- ---- ----
				---- ba-- ---- ----		**
				---- --98 7654 3210		Y

** ? both bits set means "Row Sprite" if the single-sprite type hasn't been
     specified in the sprites list ?

	There are 8 scroll values for the tilemap sprites, in the
	1c0000-1c003f area (each scroll value uses 8 bytes):

	Offset: 	Bits:					Value:

		0.w								Scroll X

		2.w								Scroll Y

		4.w								? 0000, 05ff, 057f

		6.w		fed- ---- ---- ----		Tilemap width (games only use 1 -> $200, 2 -> $400)
				---c ---- ---- ----		?
				---- b--- ---- ----		Shadow (Highlight?)
				---- -a98 ---- ----		Each bit enables 2 bitplanes*
				---- ---- 7654 3210		? some games leave it to 0, others
										  use e.g 28 for scroll 0, 29 for
										  scroll 1, 2a etc.

	Where scroll x&y refer to a virtual $8000 x $200 tilemap (filling the
	whole spriteram) made of 16x16 tiles. A tile uses 4 bytes:

	Offset: 	Bits:					Value:

		0.w								Code (low bits)***

		2.w		f--- ---- ---- ----		Flip X
				-e-- ---- ---- ----		Flip Y
				--dc ba-- ---- ----		Code (high bits)
				---- --9- ---- ----		Code? Color?
				---- ---8 7654 3210		Color code (64 color steps)

	The tilemap is stored in ram by column.

*** The tiles size is (always?) 16x16 so Code and Code+1 are used.


	Note that there is a "background layer": a series of tilemap sprites
	that fill up the screen and use scroll 0 as the source tilemap are
	always displayed before the sprites in the sprites list.


Note: press Z to show some info on each sprite (debug builds only)

***************************************************************************/

#include "driver.h"
#include "vidhrdw/generic.h"
#include "seta.h"

VIDEO_START( ssv )
{
	Machine->gfx[0]->color_granularity = 64; /* 256 colour sprites with palette selectable on 64 colour boundaries */

	alpha_set_level(0x80);	// until proper shadows are implemented

	return 0;
}

/* Scroll values + CRT controller registers */
data16_t *ssv_scroll;

int ssv_special;	// kludge for hypreac2

int ssv_tile_code[16];

int ssv_sprites_offsx, ssv_sprites_offsy;
int ssv_tilemap_offsx, ssv_tilemap_offsy;

/***************************************************************************

	CRT controller, registers that are read
	(vblank etc.?)

				1c0000 (wait for bit .. to become ..)

	keithlcy:	bit D, 0 -> 1

	mslider:	bit A, 0

	hypreact:
	meosism:
	srmp7:
	sxyreact:
	ultrax:		bit F, 0

	twineag2:
	hypreac2:	bit C, 1 -> 0
				bit F, 0

	janjans1:
	srmp4:
	survarts:	No checks

	ryorioh:
	drifto94:	bit D, 0 -> 1
				bit A, 0


	CRT controller, registers that are written
	(resolution, visible area, flipping etc. ?)

				1c0060-7f:

	drifto94:	0000 0025 00cd 01c6 - 0001 0013 0101 0106
				0300 0711 0500 0000 - 0015 5940 0000 0000
				03ea      5558	(flip)

	hypreact:	0021 0022 00cb 01c6 - 0001 000e 00fe 0106
				0301 0000 0500 c000 - 0015 5140 0000 0000
				03f0      5558	(flip)

	hypreac2:	0021 0022 00cb 01c6 - 0001 000e 00fe 0106
				0301 0000 05ff c000 - 0015 5140 0000 0000
				03ea      5558	(flip)

	janjans1:	0021 0023 00cb 01c6 - 0001 000f 00fe 0106
				0300 0000 0500 c000 - 0015 5140 0000 0000
				same!	(flip)

	keithlcy:	002b 0025 00cd 01c6 - 0001 0013 0101 0106
				0300 0711 0500 0000 - 0015 5940 0000 0000
				03ea      5558	(flip)

	meosism:	002b 002c 00d5 01c6 - 0001 0012 00fe 0106
				0301 0000 0500 c000 - 0015 5140 0000 0000
				(no flip)

	mslider:	0021 0026 00d6 01c6 - 0001 000e 00fe 0106
				03f1 0711 5550 c080 - 0015 5940 0000 0000
				0301      0500	(flip)

	ryorioh:	0021 0023*00cb 01c6 - 0001 000f 00fe 0106
				0300 0000 0500 c000 - 0015 5140 0000 0000
				03ed      5558	(flip) *0025

	srmp4:		002b 002c 00d4 01c6 - 0001 0012 0102 0106
				0301 0711 0500 0000 - 0015 4940 0000 0000
				ffe8      5557	(flip)

	srmp7:		002b 002c 00d4 01c6 - 0001 000e 00fd 0106
				0000 0000 e500 0000 - 0015 7140 0000 0000
				02f2      b558	(flip)

	stmblade:	0021 0026 00d6 01c6 - 0001 000e 00fe 0106
				03f1 0711 5550 c080 - 0015 5940 0000 0000 <- 711 becomes 0 during gameplay
				0301      0500	(flip)

	sxyreact:	0021 0022 00cb 01c6 - 0001 000e 00fe 0106
				0301 0000 0500 c000 - 0015 5140 0000 0000
				03ef      5558	(flip)

	survarts:	002b 002c 00d4 01c6 - 0001 0012 0102 0106
				0301 0000 0500 0000 - 0015 5140 0000 0000
				03e9      5558	(flip)

***************************************************************************/

READ16_HANDLER( ssv_vblank_r )
{
	if (cpu_getvblank())
		return 0x2000 | 0x1000;
	else
		return 0x0000;
}

WRITE16_HANDLER( ssv_scroll_w )
{
	COMBINE_DATA(ssv_scroll + offset);

/*	offsets 60-7f: CRT Controller	*/

}

WRITE16_HANDLER( paletteram16_xrgb_swap_word_w )
{
	int r, g, b;
	data16_t data0, data1;

	COMBINE_DATA(paletteram16 + offset);

	offset &= ~1;

	data0 = paletteram16[offset + 1];
	data1 = paletteram16[offset];

	r = data0 & 0xff;
	g = data1 >> 8;
	b = data1 & 0xff;

	palette_set_color(offset>>1, r, g, b);

	if (!(Machine->drv->video_attributes & VIDEO_NEEDS_6BITS_PER_GUN))
		usrintf_showmessage("driver should use VIDEO_NEEDS_6BITS_PER_GUN flag");
}

/***************************************************************************


								Sprites Drawing

[mslider]
"Insert coins"			101f60: 0006 0825 00b0 000c
						104128: 1a3a 0000 63d4 0400 (16x16)

Character tilemap		100080: 000f 0410 0000 0000
						102080: 0002 0000 6200 0c00
								0002 0000 6200 0c40
								0002 0000 6200 0c80
								0002 0000 6200 0cc0
								0002 0000 6200 0d00
								..
								0002 0000 6200 0fc0
						1c0010:	73f0 00f1 05ff 4600


[hypreact]
intro					100140: 6003 04ca 0000 0000 (tilemap sprite)
						102650: 0003 0000 0000 0c00
								0003 0000 0000 0c40
								0003 0000 0000 0c80
								0003 0000 0000 0cc0
						1c0018:	15f8 00e8 057f 2600

game					100058: 6003 00db 0050 0040 (normal sprite)
						1006d8: 037c 001b 6400 0400

tiles					100060: 6019 0120 0014 000a	(sometimes 6619!)
						100900: 0a8c 0012 6400 0420 (32x16)
								0400 0012 6400 0800 (32x32)
								...

[hypreac2]
"warning"				100f60: 6106 3893 0068 00c8 (128x32)
						11c498: 00e0 00b2 6c00 0800
								0000 0000 0000 0000
text below "warning"	100f70: 6016 389b 0048 00b0 ((16 or 8)x8)
						11c4d8: 0054 0007 6000 0000

black regions			100af8: 6303 2d64 0000 03f8 (yoffs should be used)
						116b20: 0004 0000 0000 0fa0 <- move up and down
								0004 0000 0000 0fe0
								0004 0000 0000 0ce0
								0004 0000 0000 0d20
						1c0020:	6c00 00ef 057f 2600

"credits" 				1012f0: 6007 440e 00e0 0008 (16x8)
						122070: 0043 0006 6000 0000

tiles					100ce8:	6111 3464 0008 0030 (16x32,empty tile frames)
						11a320: 0460 006b 6110 0800
								0460 006b 6100 0800
								..
						100d68:	6205 34de 0008 0030 (16x32, tiles on frames)
						11a6f0: 050c 0059 6000 0800
								04c0 005a 6010 0800
								04d4 005a 6020 0800
								0500 0059 6030 0800
								..
						100cf8:	6105 348a 0008 fff8 (16x16 x 2x3, big tiles below)
						11a450: 61d6 0059 6000 0420
								61f2 0059 6000 0410
								6212 0059 6000 0400
								61d8 0059 6010 0420
								61f4 0059 6010 0410
								6214 0059 6010 0400

[keithlcy]
high scores				101030:	717f 40c0 0010 0000
						120600:	0000 0000 00c0 0025 (16x16)
								0000 0000 00d0 0025
								..
								0000 0000 0000 ffff (ysize should be 16!)
								0000 0000 0010 ffff
								..

K of "KEITH"			101180:	610e 4600 0020 0090
						123000:	4ef4 016a 0000 0040 (16x16)
								4ef6 016a 0010 0040
								..

floating robot (demo)	101000:	713d 4000 03b0 0088
						120000:	..
								71f6 0020 0000 0030
								71f8 0020 0010 0030
								..

cityscape				100030: 7304 1600 0000 007c (yoffs should not be used)
						10b000: 0001 0000 0200 0000
								0001 0000 0200 0040
								0001 0000 0200 0080
								0001 0000 0200 00c0
						1c0008:	0800 00f2 05ff 5729


[meosism]
shadows					100100: 701f 051b 0041 0020 (16x16 shadow)
						1028d8: 05aa 0030 f000 0470

[srmp4]
logo					100000: 6303 1680 0180 0078 (yoffs?)
						10b400: 0001 0000 0000 0060
								0001 0000 0000 0020
								0001 0000 0000 ffe0
								0001 0000 0000 ffa0
						1c0008:	0800 00ec 05ff 5629

tiles					100088: 6103 25b7 0028 000a (16x16)
						112db8: f4aa 0009 03f8 0018
								f4a8 0009 0008 0018
								f4ba 0009 03f8 0008
								f4bc 0009 0008 0008

[survarts]
tilemap					100030: 6303 2048 0000 0000
						110240: 0002 0000 0160 03fc
								0002 0000 0160 003c
								0002 0000 0160 007c
								0002 0000 0160 00bc
						1c0010:	0c2e 01f5 05ff 4628

player					100030: 611f 1da0 0000 fffc
						10ed00: eb16 200f 005c fffa (16x16)

"push start"			100130: 601d 1920 0048 0000
						10c900: 0441 0004 0000 004c (16x8)

[drifto94]
car shadow				100010: 8137 0640 0080 0030
						103200: ..
								544a 21e4 0030 0030 (16x16)

writings on finish		100130: 6109 4840 004e 0058 "good work"
						124200: ee6e 0135 0024 0000 (16x16)
						100158: 611e 4860 0058 0020 "you have proved yOur"..
						124300: ee92 0137 0024 0014 (16x16)
								..
								ee7e 0137 fff4 0000 (16x16!!)	; 'O'
								..

[ultrax]
sprite begin of lev1	100010:	6b60 4280 0016 00a0
						121400:	51a0 0042 6800 0c00 (64x64)

From the above some noteworthy cases are:

			101f60: 0006 0825 00b0 000c
			104128: 1a3a 0000 63d4 0400		consider y size & depth

			101030:	717f 40c0 0010 0000
			120600:	0000 0000 0000 ffff		ignore y size & depth

			100158: 611e 4860 0058 0020
			124300	ee7e 0137 fff4 0000		ignore x size & depth

			100f60: 6106 3893 0068 00c8
			11c498: 00e0 00b2 6c00 0800		consider x size & y size

			100100: 701f 051b 0041 0020
			1028d8: 05aa 0030 f000 0470		consider depth

			100010:	6b60 4280 0016 00a0
			121400:	51a0 0042 6800 0c00

			100140: 6003 04ca 0000 0000		tilemap
			102650: 0003 0000 0000 0c00

			100080: 000f 0410 0000 0000		tilemap
			102080: 0002 0000 6200 0c00

**************************************************************************/

/* Draw a tilemap sprite */

static void ssv_draw_row(struct mame_bitmap *bitmap, int sx, int sy, int scroll)
{
	struct rectangle clip;
	int attr, code, color, mode, size, page, shadow;
	int x, x1, sx1, flipx, xnum, xstart, xend, xinc;
	int y, y1, sy1, flipy, ynum, ystart, yend, yinc;
	data16_t *s3;

	xnum	=		0x20;		// width in tiles (screen-wide)
	ynum	=		0x8;		// height in tiles (always 64 pixels?)

	scroll	&=		0x7;		// scroll register index

	/* Sign extend the position */
	sx = 0;
	sy = (sy & 0x1ff) - (sy & 0x200);

	/* Set up a clipping region for the tilemap slice .. */

	clip.min_x = sx;
	clip.max_x = sx + xnum * 0x10 - 1;
	clip.min_y = sy;
	clip.max_y = sy + ynum * 0x8  - 1;

	/* .. and clip it against the visible screen */

	if (clip.min_x > Machine->visible_area.max_x)	return;
	if (clip.min_y > Machine->visible_area.max_y)	return;

	if (clip.max_x < Machine->visible_area.min_x)	return;
	if (clip.max_y < Machine->visible_area.min_y)	return;

	if (clip.min_x < Machine->visible_area.min_x)	clip.min_x = Machine->visible_area.min_x;
	if (clip.max_x > Machine->visible_area.max_x)	clip.max_x = Machine->visible_area.max_x;

	if (clip.min_y < Machine->visible_area.min_y)	clip.min_y = Machine->visible_area.min_y;
	if (clip.max_y > Machine->visible_area.max_y)	clip.max_y = Machine->visible_area.max_y;

	/* Get the scroll data */

	x		=	ssv_scroll[ scroll * 4 + 0 ];	// x scroll
	y		=	ssv_scroll[ scroll * 4 + 1 ];	// y scroll
//				ssv_scroll[ scroll * 4 + 2 ];	// ? 0, 05ff, 057f
	mode	=	ssv_scroll[ scroll * 4 + 3 ];	// shadow, depth etc.

	/* How is the background layer disabled ? */
	if ((mode & 0x0700) == 0)	return;

	shadow	=	(mode & 0x0800);

	/* Decide the actual size of the tilemap. $200 and $400 pixels
	   are the only values actually used AFAIK */
	size	=	1 << (8 + ((mode & 0xe000) >> 13));
	page	=	(x & 0x7fff) / size;

	/* Given a fixed scroll value, the portion of tilemap displayed changes
	   with the sprite postion */
	x	+=	sx;
	y	+=	sy;

	/* Tweak the scroll values (game specific) */
	x	+=	ssv_tilemap_offsx;
	y	+=	ssv_tilemap_offsy;

	/* Draw the rows */

	x1	=	x;
	y1	=	y;
	sx1	=	sx - (x & 0xf);
	sy1	=	sy - (y & 0xf);

	for (sx=sx1,x=x1; sx <= clip.max_x; sx+=0x10,x+=0x10)
	{
		for (sy=sy1,y=y1; sy <= clip.max_y; sy+=0x10,y+=0x10)
		{
			int tx, ty, gfx, transparency;

			s3	=	&spriteram16[	page * (size * ((0x1000/0x200)/2))	+
									((x & ((size -1) & ~0xf)) << 2)	+
									((y & ((0x200-1) & ~0xf)) >> 3)		];

			code	=	s3[0];	// code high bits
			attr	=	s3[1];	// code low  bits + color

			/* Code's high bits are scrambled */
			code	+=	ssv_tile_code[(attr & 0x3c00)>>10];
			flipy	=	(attr & 0x4000);
			flipx	=	(attr & 0x8000);
			color	=	attr;

			/* Select 256 or 64 color tiles */
			gfx	=	((mode & 0x0100) ? 0 : 1);

			/* Force 16x16 tiles ? */
			if (flipx)	{ xstart = 1-1;  xend = -1; xinc = -1; }
			else		{ xstart = 0;    xend = 1;  xinc = +1; }

			if (flipy)	{ ystart = 2-1;  yend = -1; yinc = -1; }
			else		{ ystart = 0;    yend = 2;  yinc = +1; }

			transparency = shadow ? TRANSPARENCY_ALPHA : TRANSPARENCY_PEN;

			/* Draw a tile (16x16) */
			for (tx = xstart; tx != xend; tx += xinc)
			{
				for (ty = ystart; ty != yend; ty += yinc)
				{
					drawgfx( bitmap,	Machine->gfx[gfx],
										code++,
										color,
										flipx, flipy,
										sx + tx * 16, sy + ty * 8,
										&clip,
										transparency ,0 );
				} /* ty */
			} /* tx */

		} /* sy */
	} /* sx */

}

/* Draw the "background layer" using multiple tilemap sprites */

static void ssv_draw_layer(struct mame_bitmap *bitmap)
{
	int sy;
	for ( sy = 0; sy <= Machine->visible_area.max_y; sy += 0x40 )
		ssv_draw_row(bitmap, 0, sy, 0);
}

/* Draw sprites in the sprites list */

static void ssv_draw_sprites(struct mame_bitmap *bitmap)
{
	/* Sprites list */

	data16_t *s1	=	spriteram16;
	data16_t *end1	=	spriteram16 + 0x02000/2;
	data16_t *end2	=	spriteram16 + 0x40000/2;
	data16_t *s2;

	for ( ; s1 < end1; s1+=4 )
	{
		int attr, code, color, num, sprite;
		int sx, x, xoffs, flipx, xnum, xstart, xend, xinc;
		int sy, y, yoffs, flipy, ynum, ystart, yend, yinc;
		int mode,global_depth,global_xnum,global_ynum;

		mode	=		s1[ 0 ];
		sprite	=		s1[ 1 ];
		xoffs	=		s1[ 2 ];
		yoffs	=		s1[ 3 ];

		/* Last sprite */
		if (sprite & 0x8000) break;

		/* Single-sprite address */
		s2		=		&spriteram16[ (sprite & 0x7fff) * 4 ];

		/* Every single sprite is offset by x & yoffs, and additionally
		   by one of the 8 x & y offsets in the 1c0040-1c005f area   */

		xoffs	+=		ssv_scroll[((mode & 0x00e0) >> 4) + 0x40/2];
		yoffs	+=		ssv_scroll[((mode & 0x00e0) >> 4) + 0x42/2];

		/* Number of single-sprites (1-32) */
		num				=	(mode & 0x001f) + 1;
		global_ynum		=	(mode & 0x0300) << 2;
		global_xnum		=	(mode & 0x0c00);
		global_depth	=	(mode & 0xf000);

		for( ; num > 0; num--,s2+=4 )
		{
			int depth, local_depth, local_xnum, local_ynum;

			if (s2 >= end2)	break;

			sx		=		s2[ 2 ];
			sy		=		s2[ 3 ];

			local_depth		=	sx & 0xf000;
			local_xnum		=	sx & 0x0c00;
			local_ynum		=	sy & 0x0c00;

			depth = global_depth ? global_depth : local_depth;
			xnum = local_xnum;
			ynum = local_ynum;

			if (global_depth && global_depth != local_depth)
			{
				if (global_xnum || global_ynum)
				{
					xnum = global_xnum;
					ynum = global_ynum;
				}
				else
					depth = local_depth;
			}

			if ( xnum == 0 && ynum == 0x0c00 )
			{
				int scroll;

				scroll	=		s2[ 0 ];	// scroll index
//								s2[ 1 ];	// always 0
//								s2[ 2 ];	// ignore x offset?
//								s2[ 3 ];	// ignore y offset?

				// Kludge for srmp4
				if (ssv_scroll[0x7a/2] == 0x4940)	sy+=0x60;

				ssv_draw_row(bitmap, sx, sy, scroll);
			}
/* 	"normal" sprite
	hot spots:
	"warning" in hypreac2 has mode & 0x0100 and is not 16x16
	keithlcy high scores has mode & 0x0100 and y & 0x0c00 can be 0x0c00
	drifto94 "you have proved yOur".. has mode & 0x0100 and x & 0x0c00 can be 0x0c00
	ultrax (begin of lev1):	100010:	6b60 4280 0016 00a0
							121400:	51a0 0042 6800 0c00	needs to be a normal sprite
*/
			else
			{
				int shadow, gfx, transparency;
				if (s2 >= end2)	break;

				code	=	s2[0];	// code high bits
				attr	=	s2[1];	// code low  bits + color

				/* Code's high bits are scrambled */
				code	+=	ssv_tile_code[(attr & 0x3c00)>>10];
				flipy	=	(attr & 0x4000);
				flipx	=	(attr & 0x8000);
				color	=	attr;

				/* Select 256 or 64 color tiles */
				gfx		=	(depth & 0x1000) ? 0 : 1;
				shadow	=	(depth & 0x8000);

				/* Single-sprite tile size */
				xnum = 1 << (xnum >> 10);	// 1, 2, 4 or 8 tiles
				ynum = 1 << (ynum >> 10);	// 1, 2, 4 tiles (8 means tilemap sprite?)

				if (flipx)	{ xstart = xnum-1;  xend = -1;    xinc = -1; }
				else		{ xstart = 0;       xend = xnum;  xinc = +1; }

				if (flipy)	{ ystart = ynum-1;  yend = -1;    yinc = -1; }
				else		{ ystart = 0;       yend = ynum;  yinc = +1; }

				/* Apply global offsets */
				sx	+=	xoffs;
				sy	+=	yoffs;

				/* Sign extend the position */
				sx	=	(sx & 0x1ff) - (sx & 0x200);
				sy	=	(sy & 0x1ff) - (sy & 0x200);

				/* Tweak it (game specific) */
				if (ssv_special == 2) sy = 232 - sy; // vasara, wheres the register for this?

				sx	=	ssv_sprites_offsx + sx;
				if (ssv_scroll[0x74/2] & 0x8000)	// srmp7, twineag2, ultrax
					sy	=	ssv_sprites_offsy + sy;	// ?
				else
					sy	=	ssv_sprites_offsy - sy - (ynum-1) * 8;

				/* Draw the tiles */
				transparency = shadow ? TRANSPARENCY_ALPHA : TRANSPARENCY_PEN;

				for (x = xstart; x != xend; x += xinc)
				{
					for (y = ystart; y != yend; y += yinc)
					{
						drawgfx( bitmap,	Machine->gfx[gfx],
											code++,
											color,
											flipx, flipy,
											sx + x * 16, sy + y * 8,
											&Machine->visible_area,
											transparency, 0 );
					}
				}

				#ifdef MAME_DEBUG
				if (keyboard_pressed(KEYCODE_Z))	/* Display some info on each sprite */
				{	struct DisplayText dt[2];	char buf[10];
					sprintf(buf, "%02X",/*(s2[2] & ~0x3ff)>>8*/mode>>8);
					dt[0].text = buf;	dt[0].color = ((s1[0] & 0x0200) ? UI_COLOR_INVERSE : UI_COLOR_NORMAL);
					dt[0].x = sx;		dt[0].y = sy;
					dt[1].text = 0;	/* terminate array */
					displaytext(Machine->scrbitmap,dt);		}
				#endif

			}		/* sprite type */

		}	/* single-sprites */

	}	/* sprites list */
}


/***************************************************************************


								Screen Drawing


***************************************************************************/

static int enable_video;

void ssv_enable_video(int enable)
{
	enable_video = enable;
}

VIDEO_UPDATE( ssv )
{
	/* The background color is the first one in the palette */
	fillbitmap(bitmap,Machine->pens[0],&Machine->visible_area);

	if (!enable_video)	return;

	ssv_draw_layer(bitmap);		// "background layer"
	ssv_draw_sprites(bitmap);	// sprites list
}
